Azimuth stabilizer



g- 9, 1955 L. B. M. BUCHANAN 2,714,837

AZIMUTH STABILIZER I Filed April 25, 194'? a 4 FIE J 2 REVERSIBLE HYDEHUL IC MOTOR AZEMUTH STABILIZER Leslie 13. M. Buchanan, Wilbraharn, Mass.

Application April 23, 1947, Serial No. 743,287

3 Claims. (Cl. 89-41) This invention relates to an azimuth stabilizing and control system intended more particularly for use in controlling the training of a gun mounted upon a tank or other vehicle. The main gun or guns of a tank are conventionally mounted in a turret, the gun and turret being trained as a unit. The gun is mounted for elevation with respect to the turret or other rotatable support. When the gun is being fired at a target while the vehicle is in motion, any yaw or change of course of the vehicle, requires an equal and opposite angular movement of the gun relatively thereto. At the same time, unless the course of the vehicle is directly toward or away from the target, the translation of the vehicle requires an additional slow angular motion to maintain the gun aimed at the target.

It is accordingly an object of the invention to provide a power driven system or" azimuth control wherein the gun is automatically moved relatively to the vehicle to maintain it trained upon the target while, at the same time, the slow training motion necessitated by the translational movement of the vehicle discussed in the preceding paragraph, may be manually introduced.

A further object is the provision of a system wherein both corrective movements are introduced by a gyroscope automatically responsive to yaw or change in course of the tank.

A still further object is the provision of a hydraulicallyoperated power drive wherein the rate of training will be proportional to the displacement of a slidable element of a pump, together with connections between the gyroscope and pump operating to displace the aforesaid element by an amount substantially proportional to the angle of precession of the gyroscope and, hence, to the rate of turning or yaw of the vehicle.

Other objects and advantages will become apparent as the description proceeds.

In the drawing,

Figure 1 is a diagrammatic view of the system of my invention, showing in section a portion of the pump and slide block control, the general service pump and control, the gyroscope, and hydraulic and electrical connections between the parts, and

Figure 2 is an elevation, partly in section, of a gyroscope suitable for use with the invention together with the control handle therefor.

Referring in detail to the drawings, 1 identifies a hydraulic motor having a pinion 2 on its shaft, in mesh with a ring gear 3, a small portion only of which is shown. Preferably, the ring gear 3 is fined to the tank adjacent to and extending 360 about the turret track. The motor 1 is then carried by the turret so that on rotation, the motor moves the turret and its guns in train. The motor is of any well-known reversible type such as a radial piston type and is connected by conduits 4 and 5 with the pressure and exhaust outlets of a pump, generally identified by the numeral 6. For the purpose of illustration, this pump has been shown as of the well-known type having a power-driven rotor 7 having radial pistons 8, the

atent ice outer ends of which contact the inner race 9 of a bearing 10 whose rollers engage the inner periphery of the chamber of slide block 11. The slide block is mounted for limited translation in the horizontal direction, as seen in Figure 1, relatively to pump casing 12, by antifriction bearings 13 and 14. Translation of slide block 11 varies the eccentricity of the axis of bearing 10 relatively to the axis of rotor 7 and thus varies the stroke of pistons 8 and the rate of delivery of the pump for a given rotor speed. As is well known, when slide block 11 is displaced so that the axis of bearing 19 is to the right of the axis of rotor 7, the pump discharges through conduit 4 and drives motor 1 in one direction of rotation. Conversely, when the slide block is displaced so that the axis of bearing 10 is to the left of the axis of rotor 7, the pump discharges through conduit 5 and rotates motor 1 in the opposite direction. Under all conditions of adjustment, the rate of discharge for a given pump speed is proportional to the aforesaid eccentricity.

The pump is adapted for alternative manual or automatic control. However, since the manual control forms no part of the present invention and is rendered ineffective when the pump is to be automatically controlled, as disclosed in my co-pending application Serial Number 743,286, filed April 23, 1947, such control has not been shown. When in automatic control, displacement of slide block 11 is effected by forces hydraulically applied to a rod 15 fixed thereto at one end and projecting into a cylinder block 16 attached to casing 12. This block is formed to provide a first cylinder 17 and a second and smaller cylinder 18. The two cylinders are separate and preferably axially aligned. Rod 15 extends into both cylinders and carries pistons 19 and 2i) fitting cylinders 17 and 13, respectively. The outer end of the rod fits a small cylinder 21 in a cap 22 closing the end of cylinder 18. A conduit 23 connects this cylinder with the interior 1 of casing 12 to compensate for the pressure in the casing,

otherwise tending to translate the rod 15 and slide block to the left as viewed in Figure 1. A pair of light coil springs 24 and 25 are interposed as shown between the piston 19 and the respective ends of the cylinder 17.

'- These springs may be slightly pre-stressed and thus act to urge the slide block into central or no-delivery position. In the figure, the slide block is shown at substantially its central or no-delivery position. A branch conduit 4a connects conduit 4 with cylinder 13 on one side of piston 20 while a second branch conduit 5a connects conduit 5 with cylinder 18 upon the other side of piston 20. The purpose of this connection will be subsequently explained.

At 26 is indicated generally a general service pump and fluid pressure control. This unit is of conventional and Well known construction and is described in detail in the patent to Frank W. Taylor, 2,381,162, Aug. 7, 1945, for Hydraulic System for Stabilizers. Consequently, it is deemed sufficient merely to identify casing 27, gear pump 28, teeter-bar 29, valves 30 and 31 connected with opposite ends of said bar and reciprocably 1; bar 29 is tilted clockwise, valve element 31 is moved to restrict the flow of pressure fluid from its orifice, while valve element 30 is moved to increase the effective area of its orifice and to decrease the resistance to fiuid'flow therefrom. As a result, pressure builds up in conduit 35 and is reduced in conduit 34, and piston 19 and slide 19 block 11 are urged leftwardly to cause pump 6 to discharge through conduit 5, drive motor 1 and train the gun in a corresponding direction of rotation. In a like manner, when the pull of magnet 32 predominates over that of 33, fluid pressure is built up in conduit 34.0ver that in 35 and the slide block is moved to the right to reverse the direction of discharge of the pump.

Energization of electromagnets 32 and 33 is effected by leads 36, 37 and 38 extending through the wall of casing 27. Lead 36 is a common grounded return for both magnets. The other leads 37 and 38 are connected to the respective center terminals of a doublepole double-throw switch 39. One pair of outer terminals of switch 39 are connected by leads 40 and 41 to the respective ends of a slewing potentiometer 42 whose contact element 43 is connected by lead 44 with a source of D. C. voltage. Element 43 has a handle 45 by which it may be turned. Preferably, a centralizing spring of well-known construction, not shown, is provided to urge element 43 into the central or neutral position shown so that, when released, it automatically returns to such position. Thus, when switch 39 is closed to the left as viewed in Figure 1, turning of element 43 in one direction or the other effects a corresponding differential energization of magnets 32 and 33 in proportion to such turning and a corresponding displacement of slide block 11 and pump discharge. In this manner, the gun may be rapidly trained upon the target under manual control, after which the switch may be closed to the right to effect automatic control in the manner to be described.

Automatic stabilization of the gun in azimuth, is effected by a rate responsive gyroscope identified in general by numeral 46. The gyroscope is mounted upon a normally horizontal base 47 which may be mounted, either in the hull of the tank or other vehicle or, alternatively, in the turret. A forked standard 48 is secured to and rises from base 47. The upper ends of the standard carry aligned bearings 49, only one of which is shown in the drawing. These bearings define a normally horizontal precession axis perpendicular to the plane of the drawing. The gyro casing 50 carries aligned trunnions 51 journaled in bearings 49. The casing 50 may be that of an ordinary D. C. or A. C. motor whose rotor shaft 52 turns on a normally horizontal axis perpendicular to and intersecting the aforesaid precession axis. To increase the moment of inertia of the spinning parts, a flywheel 53 is fixed to the projecting end of shaft 52. The gyroscope casing and parts mounted upon or carried thereby are so designed that the center of gravity of the combined parts lies at the intersection of the precession and spin axes. The gyroscope is thus said to be in neutral equilibrium in that, in the absence of an externally applied force or torque, it has no tendency to move from any given position about the axis of precession.

Base 47 has a bearing bracket 54 fixed thereto. A shaft 55 is journaled in a bearing in bracket 54 on an axis parallel to that of trunnions 51, and has a pinion 56. Manually operated means conventionally shown as a handle 57 are fixed to shaft 55. It will be understood that any known electrical or mechanical remote control mechanism may be used to rotate shaft 55 as desired.

The pinion 56 meshes with an arcuate rack section 58 attached to the outer periphery of an arcuate tube section 59 having closed ends. Tube section 59 is carried by arms 60 and 61 which extend radially of the axis of trunnions 51 and are attached at their inner ends to a hub 62 journaled on standard 48 coaxially of but separate from the adjacent trunnion 51. The tube and rack are, of course, concentric about the aforesaid trunnion axis and preferably, but not necessarily, lie in the vertical plane through the spin axis of shaft 52 and flywheel 53. The tube section is slotted along its inner periphery, as at 63 so that the laterally projecting finger 64 of a bracket 65,\may pass freely therethrough. This bracket is fixed to casing 50.

A spring 66 is interposed between finger 64 and the lower closed end of tube 59. Likewise, a second spring 67 is interposed between the finger 64 and the upper closed end of tube 59. These springs may be pre-stressed so that, on turning of handle 57 and shaft 55 in either direction, they act through finger 64 to apply a torque suflicient to pivot the gyroscope about the axis of trunnions 51. The drive from handle 57 to tube section 59 is irreversible so that precession of the gyroscope is incapable of turning shaft 55. As a result, the spring 66 and 67 act to constrain or yieldingly resist precession and the angle of precession will thus be substantially proportional to the rate of change of course or yaw, that is, to the angular rate of movement of the tank about its normally vertical axis. The direction of precession will depend upon the direction of yaw or change of course. Thus, for a direction of spin as indicated by the arrow on flywheel 53, Figure 2, the precession will be counterclockwise as viewed in Figure 2, for a yaw or turn to the right. turn to the left will produce a clockwise direction of precession.

The gyroscope has fixed thereto an upstanding arm- 63 which carries at its top a spacer 69 of dielectric material such as Micarta. This spacer extends between the opposite sets of leaves 70 and 71 of a variable resistance called a silverstat. This type ofresistance is well known as is disclosed in the aforesaid patent to. Taylor. Hence it is deemed sufficient to point out that,

when in initial or mid position, an equal number ofleaves of the two sets are held in contact by the spacer 69, so that the effective resistances of the resistors 72 and 73 are equal. either direction it moves spacer 69 to bring additional leaves of one set into engagement and thereby short out a corresponding number of sections of that resistor. At the same time leaves of the other set, previously in contact, are separated thereby increasing the eifective resistance in the circuit of the corresponding resistor. switch 39 thrown to the right, Figure l, the energization of magnets 32 and 33 is differentially varied, as will be understood from inspection of the figure.

Resistors 72 and 73 have a common terminal 74 connected With a sensitivity rheostat 75 whose slider is connected by lead 76 with a source of D. C. voltage.

From the other terminal of resistor 72, a line 77 extends.

to one terminal of switch 39. A line 78 connected the other terminal of resistor 73 with the remaining terminal of switch 39. Thus, when switch 39 is thrown to the right as viewed in Figure l, the gun is placed under automatic, or gyroscopic, control.

The operation when switch 39 is thrown to the left and the general service pump thus placed under simple manual control has been previously explained. When the switch is thrown to the right and assuming that the gun has been previously properly aimed, any angular movement of the tank, such as that produced by yaw or change of course, will cause a precession or angular movement of the gyroscope 46, about the trunnions 51. In all cases, the direction of precession will be in a direction corresponding with the direction of turn. That is to say, for turn or yaw to the right, the gyroscope will precess in one direction and for a turn to the left will precess in the opposite direction, the particular directions depending upon the direction of spin of the gyro rotor. Because of the constraint afforded by springs 66 and 67, the angle of precession in all cases is substantially proportional to the rate of angular movement of the vehicle in azimuth. Within the limits of its operating range, the

silverstat and general service pump 36 are so designed:

and coordinated, that the delivery pressure differences of the pump are substantially directly proportional to the difference in the number of silverstat leaves closed.

at any time. Since this number is determined by the angle of precession of the gyroscope, the displacement.

of the slide block 11 and the corresponding rate of dis- Conversely, a

However, as the gyroscope precesses in With charge of pump 6 may be made closely directly proportional to the angle of precession. Since the response of the parts to angular movement about the vertical is practically instantaneous and the gyroscope remains in precessed position as long as the turning exists, the effect is to turn the gun by an angle equal to the time integral of the rate of angular movement of the vehicle, in short, by an angle relatively to the vehicle, equal to the total angle of vehicular change of heading. The connections being such that the training movement of the gun relatively to the tank is opposite to the change of heading of the tank, it follows that the gun is accurately stabilized in azimuth.

The foregoing explanation ignores the fact that because of its mechanical construction, pump 6 has an inherent tendency to return its slide block to central or nodelivery position with a force proportional to the discharge pressure of the pump and hence proportional to displacement of the slide block from central or nodeliver position. This is true for both directions of slide block displacement. The springs 24 and 25 being compressed directly as the applied force, it follows that unless an additional force is applied to effect displacement of the slide block the increments of displacement thereof will decrease for corresponding equal increments of increase of pressure difference in conduits 34 and 35 and the rate of train would not be directly proportional to the rate of change of heading of the vehicle.

To overcome this defect, I have provided the cylinder 18 and piston 20. It has previously been explained that when the slide block is displaced to the right, for example, the pump discharges through conduit 4. Since the pressure increases with the rate of discharge, the pressure exerted on piston 20 through conduit 4:: will, under such condition, tend to displace the slide block with a force increasing with increased displacement of the slide block. By proper dimensioning of the cylinder 18 and piston 20, the force thus exerted may be made approximately equal to the aforesaid force inherently tending to centralize the slide block. The connections being such that the two forces are always in opposition, it follows that the displacement of the slide block is effected by and proportionally to, the difierence in pressures in conduits 34 and 35. Hence the rate of train of the gun will be closely equal and opposite to the instantaneous rate of change of heading of the vehicle. The gun will thus be automatically stabilized in azimuth.

When it is desired, in addition to the aforesaid stabilizing action, to impart an additional azimuthal movement to the gun, as might be made necessary, for example, by translation or linear movement of the tank or target, it is merely necessary to turn handle 57 in the corresponding desired direction. This action pivots tube section 59 about the axis of trnnnions 51 and varies the constraint exerted by spring 66 or 67, upon the gyroscope. Because the maximum angle of precession in either direction, is relatively small, the gyroscope, Whenever handle 57 is displaced, takes up a new position which, obviously, is the algebraic sum of the angular displacement of tube 59 and the instantaneous angle of precession, if any. Thus, the handle may be operated at any time, whether or not the vehicle is changing its course and the effect upon the gun will be its azimuthal stabilization as previously described, with the desired additional movement correctly algebraically added thereto.

While I have shown the form of the invention now preferred by me, various substitutions and modifications will occur to those skilled in the art after a study of the present disclosure. Hence the foregoing disclosure should be taken in an illustrative rather than a limiting sense; and it is my desire to reserve all such changes as fall within the scope of the sub-joined claims.

Having now fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. In an azimuth stabilizing and control system of the character described, adapted to be used for an object mounted for pivotal movement about a normally vertical axis on a vehicle, the combination of a hydraulic motor adapted to be operatively connected to said object to operatively effect said pivotal movement thereof, a pump connected to drive said motor, said pump having an element movable in either direction from a nodischarge position to correspondingly reverse and vary the rate of discharge of said pump, said pump acting inherently to apply a first force urging said element to no-discharge position, means responsive to the discharge pressure of said pump and connected with said element to apply a second force urging said element away from no-discharge position, said two forces being substantially equal for all positions of said element, spring means urging said element to no-discharge position, a separate source of fiuid pressure, means responsive to said fluid pressure and actuating said element against the action of said spring means, a two-degree-of-freedom constrained gyroscope adapted to be carried by said vehicle for operative precession in response to change in heading of said vehicle, and means controlled by said gyroscope to vary the effective fluid pressure of said source by and in proportion to, the angle of precession of said gyroscope.

2. An azimuthal position stabilizing and controlling system of the character described, adapted to be used for an object mounted for training about a vertical axis thereof on a vehicle, comprising, in combination, a reversible hydraulic motor adapted to be operatively connected to said object to operatively efiect said training thereof, a hydraulic pump having a slide block translatable in opposite directions from a no-discharge position to correspondingly reverse and vary the rate of, the

' discharge of said pump, said pump acting inherently to urge said block to no-discharge position, first and second fluid conduits between said pump and motor, spring means urging said block to no-delivery position, first and second cylinders associated with said pump, a piston in each cylinder, means connecting said pistons with said block, means connecting each said conduit with said first cylinder on respectively opposite sides of its piston, a source of fluid under pressure and having conduits connected to said second cylinder upon opposite sides of its piston, control means operable to diiferentially vary the pressures from said source eiiective upon opposite sides of the piston in said second cylinder, rate responsive gyroscopic means adapted to be mountably supported by said vehicle for operative precession in response to change and proportional to rate thereof in heading of said vehicle, and operative means connecting said gyroscopic means and said control means for operation of the latter gyroscopic means and said control means for operation in response to operative precession of said gyroscopic means.

3. In an azimuthal movement stabilizing and controlling system of the character described, adapted to be used for an object mounted for training about a normally vertical axis thereof on and with respect to a vehicle, the combination of a hydraulic motor adapted to be operatively connected to said object to operatively efiect said training thereof, a pump including a slide block operable in each direction from a no-discharge position to vary the corresponding direction and rate of discharge of said pump, said pump inherently acting to urge said block to no-discharge position, first and second coaxial cylinders carried by said pump, a piston in each cylinder, a rod connecting said pistons and slide block, first and second discharge passageways between said pump and motor, each having a branch to said first cylinder on respective opposite sides of the piston therein to urge said block away from no-discharge position, a source of pressure fluid, conduits between said source and second cylinder, a gyroscope adapted to be supportably mounted upon said vehicle for precession in response to rate of change of heading of the vehicle, and means operated by said gyroscope in response to precession thereof to control the pressure from said source efiective in said second cylinder whereby said slide block is displaced proportional to said rate.

4. In an automatic azimuthal movement stabilization system of the character described, adapted to be used for an object mounted for azimuthal movement on and relative to a vehicle, the combination of a hydraulic motor adapted to be operatively connected to said object to operatively effect azimuthal movement thereof, the combination of a rotary piston variable displacement pump having a slide block displaceable in opposite directions from a no discharge position to correspondingly vary the direction and rate of discharge of said pump, a hydraulic connection between said pump and said motor for driving the latter, said pump operatively acting inherently to urge said block to no-discharge position, means responsive to the discharge pressure of said pump and operable to urge said block away from no-discharge position, spring means urging said block to no-discharge position, gyroscopic means adapted to be mountably supported on said vehicle for precession automatically in response to turning of said vehicle to apply a precession responsive force to said slide block to displace the same against the action of said spring means.

5. In an azimuthal movement stabilizing and controlling system of the character described, adapted to be used for rotating in azimuthal movement about a normally vertical axis and at a variable rate an object mounted upon a vehicle, the combination of a reversible discharge variable delivery pump including a slide block movable from no-delivery position in opposite directions to vary the corresponding direction and rate of discharge of said pump, said pump acting inherently to move said block to no-discharge position, a reversible hydraulic motor adapted to be operatively connected to said object to operatively effect said rotating thereof, first and second main pressure conduits connecting said pump and motor for driving the latter, first and second double-acting pressure responsive means, each operable to apply a force to said block, spring means urging said block to no-discharge position, a branch conduit from each said main conduit to a respective side of said first pressure responsive means whereby the discharge pressure of said pump acts to urge said block away from no-discharge position, a source of fluid pressure, conduits connecting said source to respective opposite sides of said second pressure responsive means, a gyroscope adapted to be mountably supported on said vehicle to precess in response to rate of change of heading of the latter, and control means operated by precession of said gyroscope to differentially vary the pressure of said source efiective upon said second pressure responsive means and thereby move said block against the action of said spring means.

6. A gun-stabilizing gyroscope mounted for precession about an axis comprising a casing, a rotor journaled in said casing for spinning about a first axis, a base, means mounting said casing for pivotal movement about a sec- 0nd axis normal to and concurrent with said first axis at a point, spring means connected with said casing to urge said spin axis to a definite angular position with respect to said base, a unitary mount for said spring means, means limiting said mount to movement in a direction substantially perpendicular to said precession axis in offset relation therefrom, and manually operable means to move said mount to vary said position.

7. In a gyroscope mounted for precession about an axis normal to its spin axis, a pair of springs each connected at one end with said gyroscope, each spring being adapted to be stressed by and in response to precession of said gyroscope in a respective direction of movement from a predetermined position, a unitary mount for said springs and to which the other ends are connected, said mount being movable in a path oltset from said axis and lying in a plane normal thereto, and manually operable means connected with said mount to move the same in said path, to thereby vary said position.

8 In a gyroscope, a casing, a rotor journaled in said casing for spinning about a first axis, means mounting said casing for precession about a second axis normal to and concurrent with, said first axis, an arcuate tube section slotted about its circumference and having abutments at its ends, a pair of springs in said section engaging a respective abutment at their remote ends, means mounting sald section for movement in an arcuate path substantially concentric of said second axis, an arm fixed to said casing and projecting through said slot into said section and between the confronting ends of said springs, and means manually operable to move said section in said path to thereby apply a force through said springs tending to turn said gyroscope about said second axis, said springs,

acting normally to yieldingly resist precession of said gyroscope about said axis.

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